The present invention relates to the polymerization of aliphatic diols and diacids. Polycarbonate is a thermoplastic that has excellent mechanical properties such as impact resistance, heat resistance and transparency. Polycarbonates are widely used in applications ranging from football helmets to automobile parts to transparent security windows. More recently, polycarbonates have also proven to be the material of choice for optical media applications such as optical discs, for example compact discs (CD) and digital versatile discs (DVD). Conventional polycarbonates are usually produced by (1) an interfacial polymerization, in which bisphenol A (BPA) is reacted directly with phosgene or by (2) a melt polymerization process in which BPA is transesterified with a diaryl carbonate such as diphenylcarbonate (DPC) or an activated diaryl carbonate such as bismethylsalicylcarbonate (BMSC). For many applications, there has been a need for materials possessing the fundamental characteristics of transparency and toughness inherent in BPA polycarbonate but possessing, in addition, certain physical properties provided by the use of aliphatic compounds such as aliphatic dihydroxy compounds and/or aliphatic diacid compounds.
These aliphatic compounds however have been found difficult to use in melt transesterification reactions owing to the fact that they often have low boiling points and the prior art methods for polymerizing the aliphatic compounds can lead to low molecular weight polymer and/or polymer with undesired properties due to degradation or side reactions of the monomer during polymerization. It would be extremely beneficial to find a process where high molecular weight polycarbonate can be prepared using aliphatic dihydroxy and diacid compounds where the resulting polymer has high molecular weight and useful properties.